Circuits: Current

What is the current through a wire if 240 Coulombs of charge pass through the wire in 2.0 minutes?

• 120 A

• 2.0 A

• 0.50 A

• 0.0083 A

A 1.5 volt, AAA cell supplies 750 milliamperes of current through a flashlight bulb for 5.0 minutes, while a 1.5 volt, C cell supplies 750 milliamperes of current through the same flashlight bulb for 20 minutes. Compared to the total charge transferred by the AAA cell through the bulb, the total charge transferred by the C cell through the bulb is

• half as great

• twice as great

• the same

• four times as great

The current through a lightbulb is 2.0 amperes. How many coulombs of electric charge pass through the lightbulb in one minute?

• 60 C

• 2.0 C

• 120 C

• 240 C

If 10 Coulombs of charge are transferred through an electric circuit in 5.0 seconds, then the current in the circuit is

• 0.50 A

• 2.0 A

• 15 A

• 50 A

A charge of 30 Coulombs passes through a 24 Ohm resistor in 6.0 seconds. What is the current through the resistor?

• 1.3 A

• 5.0 A

• 7.5 A

• 4.0 A

A current is said to exist whenever

• a wire is charged

• a battery is present

• electric charges are unbalanced

• electric charges move in a loop

Answer explanation

Current is the rate at which charge flows. Charge will not flow in a circuit unless there is an energy source capable of creating an electric potential difference and unless there is a closed conducting loop through which the charge can move.

Current has a direction. By convention, current is in the direction that

• positive charges move

• negative charges move

• neutral charges move

Answer explanation

By convention, the electric current direction is the direction which positive charge would move. In wires, the actual charge carriers are negatively charged electrons. Nonetheless, the convention used for the direction of current is based on the direction which positive charges would move.